EP3129419A1

EP3129419A1 - Process for the production of polyoxymethylene block copolymers

Info

Publication number: EP3129419A1
Application number: EP15712975.0A
Authority: EP
Inventors: Ilja Peckermann; Aurel Wolf; Jens Langanke; Christoph Gürtler; Jörg Hofmann
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Deutschland AG
Priority date: 2014-04-07
Filing date: 2015-04-01
Publication date: 2017-02-15
Anticipated expiration: 2035-04-01
Also published as: US10759902B2; US10093772B2; SG11201608076RA; WO2015155094A1; US20170096526A1; CN106414532A; JP6518691B2; ES2702327T3; EP3129419B1; JP2017510686A; US20180371159A1; CN106414532B

Abstract

The invention relates to a process for producing polyoxymethylene block copolymers, comprising the step of activating the DMC catalyst in the presence of an OH-terminated polymeric formaldehyde starter compound by means of a defined amount of alkylene oxide, optionally followed by polymerization with alkylene oxides, if necessary in the presence of other comonomers. The invention further relates to polyoxymethylene block copolymers that can be obtained by means of such a process and to the use of same for producing polyurethane polymers.

Description

Process for the preparation of polyoxymethylene block copolymers

The present invention describes a process for the preparation of polyoxymethylene block copolymers. It further relates to polyoxymethylene block copolymers obtainable by such a process and to their use. Block copolymers comprising polyoxymethylene units in addition to other polymer and polycondensate units are disclosed, for example, in JP 2007 211082 A, WO 2004/096746 Al, GB 807589, EP 1 418 190 A1, US Pat. No. 3,754,053, US Pat. No. 3,575,930, US 2002/0016395, and JP 04 -306215.

No. 3,575,930 describes the reaction of dihydroxy-terminated paraformaldehyde HO- (CH 2 O) _n -H where n = 2-64 with diisocyanates to form isocyanate-terminated polyoxymethylene polymers, which can be reacted in the reaction with diols to form polyurethane compounds.

JP 2007 211082 A describes the reaction of polyoxyalkylene polyols having an equivalent weight of> 2500 with formaldehyde, formaldehyde oligomers or formaldehyde polymers to polyoxymethylene-polyoxyalkylene block copolymers using anionic or cationic polymerization catalysts. The high molecular weight low polydispersity polyoxyalkylene polyol starters used are prepared via double metal cyanide (DMC) catalysis. Due to the high molecular weight of the polyoxyalkylene polyols, the resulting polyoxymethylene-polyoxyalkylene block copolymers have a molecular weight of at least> 5000 g / mol and are therefore less widely usable as a polyurethane building block.

Furthermore, the direct reaction of the polyoxyalkylene polyols with the polyoxymethylene polymers via a melt-kneading process makes the use of high temperatures and corresponding specific high-viscosity apparatuses (extruders, kneaders, etc.) necessary.

No. 3,754,053 describes polyoxymethylene-polyoxyalkylene block copolymers having a molecular weight> 10,000 g / mol. To produce copolymers having an internal polyoxymethylene block, in a first step trioxane is converted to a polyoxymethylene prepolymer and this is then reacted in the presence of e.g. NaOH reacted as a polymerization catalyst with alkylene oxides. Again, because of their high molecular weight, the polymers described are less suitable for use as polyurethane building blocks.

WO 2004/096746 Al and US 2006/0205915 Al disclose the reaction of formaldehyde oligomers with alkylene oxides and / or isocyanates. In this method, the described use of formaldehyde oligomers HO- (CH 2 O) _n -H Polyoxymethylen- Blockcopolymere obtained with a relatively narrow molecular weight distribution of n = 2-19, wherein for "

- 2 - the provision of the formaldehyde oligomers starting from aqueous formalin solution an additional thermal separation process step is required. The resulting formaldehyde oligomer solutions are not stable in storage, so that they must then be further processed immediately. In addition, these applications do not disclose any differentiated activation conditions, such as the activation temperature, of the alkoxylation catalysts used, which also have safety and quality considerations for possible industrial application by undefined temperature peaks during the exothermic polymerization process (22.7 kcal / mole PO from M. Ionesco; Chemistry and Technology of Polyols for Polyurethanes, Rapra Techn. Ltd., 2005) are disadvantageous. Furthermore, only block copolymers with very short formaldehyde blocks are accessible via this method.

EP 1 870 425 A1 discloses a process for the preparation of polyoxyalkylene-containing polyols by condensation of substituted or unsubstituted phenol structures with formaldehydes and / or other substituted alkanal structures. The resulting phenol-formaldehyde condensates are used here as polyol starters for the alkoxylation, wherein no oxymethylene repeat units are formed within these starter compounds. Furthermore, due to the different chemical structure, the resulting properties of the alkoxylated, aromatic-containing polyols fundamentally differ from aliphatic polyol structures. WO2012 / 091968 A1 claims a process for the preparation of polyetherols by polymerization of alkylene oxides on starter compounds with the aid of DMC catalysts. In this case, as formaldehyde-associated structures oligomeric phenol-formaldehyde condensates are disclosed as corresponding starter, which differs structurally fundamentally from the polyoxymethylene starter structure. Starting from the prior art, therefore, the object of providing a simple and economically advantageous method for the preparation of polyoxymethylene block copolymers based on oligomeric and polymeric forms of formaldehyde as a starter substance to provide, with which the problems resulting from the prior art overcome can be.

Here, the cleavage of the formaldehyde starter compounds used in smaller polymers, oligomers and monomers, the formation of by-products and decomposition products should be avoided as much as possible and the process safety can be increased. Furthermore, stable low-molecular weight polyoxymethylene block copolymers should be available which have hydroxy-functionalized end groups and are suitable for the reaction with di- or polyisocyanates for the preparation of polyurethanes. The process according to the invention should preferably also be suitable, polyoxymethylene-polyoxyalkylene carbonate Block copolymers accessible, with a high content of incorporated CO _{2 is} achieved.

According to the invention, this object is achieved by a process for the preparation of polyoxymethylene block copolymers by catalytic addition of alkylene oxides and optionally further comonomers to at least one polymeric formaldehyde polymer.

A starter compound having at least one terminal hydroxyl group in the presence of a double metal cyanide (DMC) catalyst, wherein

(I) in a first step, the DMC catalyst is activated in the presence of the polymeric formaldehyde starter compound, wherein for activating the DMC catalyst, a partial amount (based on the total amount of used in the activation and polymerization of alkylene oxides) of one or more Alkylene oxides is added ("activation"),

(Ii) in a second step, one or more alkylene oxides and optionally further comonomers are added to the mixture resulting from step (i), wherein the alkylene oxides used in step (ii) may be the same or different from the alkylene oxides used in step (i) ("Polymerization"), and wherein the activation of the DMC catalyst in the first step (i) takes place at an activation temperature (T _act ) of 20 to 120 ° C.

Further objects of the present invention are the polyoxymethylene block copolymers obtainable by the process according to the invention, their use and polyurethane polymers comprising the polyoxymethylene block copolymers according to the invention.

The use of the word in connection with countable quantities is here and hereinafter only to be understood as a number word if this results from the context (for example by the expression "exactly one"). Otherwise, terms such as "an alkylene oxide", " a polymeric formaldehyde starter compound, etc. always include those embodiments in which two or more alkylene oxides, two or more polymers

Formaldehyde starter compounds, etc. are used.

The invention will be explained in detail below. Various embodiments can be combined with one another as desired, as long as the opposite does not clearly result for the person skilled in the art from the context.

Polyoxymethylene block copolymers in the context of the invention are polymeric compounds which contain at least one polyoxymethylene block and at least one additional oligomer _Λ

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Block (e.g., polyoxyalkylene or polyoxyalkylene carbonate blocks) and preferably does not exceed a four-figure molecular weight.

The resulting polyoxymethylene block copolymers offer a number of advantages over existing polymers. Thus, certain physical properties, such as glass transition temperatures, melting ranges, viscosities and solubilities, etc., can be specifically controlled over the length of the polyoxymethylene blocks in relation to the other oligomeric blocks.

Compared to polyoxymethylene homopolymers of the same molecular weight, the partial crystallinity in the polyoxymethylene block copolymers according to the invention is typically reduced, which likewise usually leads to a reduction in glass transition temperatures, melting points and viscosities, etc. The presence of additional polyoxyalkylene b also typically results in a significant increase in chemical and thermal stability. In addition, the resulting polyoxymethylene block copolymers generally have good solubilities in various solvents, are usually melted easily and without mass loss, or are already present at low temperatures in the liquid state. Across from

Polyoxymethylene homopolymers thus show the polyoxymethylene block copolymers a significantly better processability.

Compared with polyether polyols of the same molecular weight, the proportion of polyoxyalkylene units which are prepared from the corresponding alkylene oxides is reduced by the proportion of polyoxymethylene, which contributes to an advantageous economy of the product. Various physical properties such as glass transition temperatures, melting ranges, viscosities, solubility, etc. can be determined for a given molecular weight over the length of the polyoxymethylene blocks in relation to the polyoxyalkylene blocks, and via the molecular weight of the polymeric formaldehyde starter compound (polyoxymethylene block) used, be targeted. The synthetic variable molecular structure of the resulting polyoxymethylene block copolymers also allows tailor-made "hard-soft" segments to be formed at the molecular level advantageous physical properties, in particular of secondary products of these

Polymers result and thus enable new applications.

Suitable polymeric formaldehyde starter compounds for the process according to the invention are in principle those oligomeric and polymeric forms of formaldehyde which have at least one terminal hydroxyl group for reaction with the alkylene oxides and optionally have further comonomers. According to the invention, the term "terminal hydroxyl group" is understood to mean in particular a terminal hemiacetal functionality which results as a structural feature via the polymerization of the formaldehyde For example, the starter compounds may be oligomers and polymers of formaldehyde of the general formula HO- (CH 2 O) _n -H, where n is an integer> 2 and wherein polymeric formaldehyde typically has n> 8 repeating units.

For the inventive method suitable polymeric formaldehyde starter compounds generally have molecular weights of 62 to 30,000 g / mol, preferably from 62 to 12,000 g / mol, more preferably from 242 to 6000 g / mol and most preferably from 242 to 3000 g / mol and include from 2 to 1000, preferably from 2 to 400, more preferably from 8 to 200 and most preferably from 8 to 100 oxymethylene repeating units. The starter compounds used in the process according to the invention typically have a functionality (F) of 1 to 3, but in certain cases they may also be more highly functional, ie have a functionality> 3. In the process according to the invention, preference is given to using open-chain polymeric formaldehyde starter compounds having terminal hydroxyl groups which have a functionality of from 1 to 10, preferably from 1 to 5, particularly preferably from 2 to 3. Very particular preference is given to using linear polymeric formaldehyde starter compounds having a functionality of 2 in the process according to the invention. The functionality F corresponds to the number of OH end groups per molecule. The preparation of the polymeric formaldehyde starter compounds which are used for the process according to the invention can be carried out by known processes (cf., for example, M. Haubs et al, 2012, Polyoxymethylene, Ullmann's Encyclopedia of Industrial Chemistry, G. Reus et al, 2012 , Formaldehyde, ibid). The formaldehyde starter compounds can in principle also be used in the form of a copolymer in the process according to the invention, 1,4-dioxane or 1,3-dioxolane being copolymerized in addition to formaldehyde as comonomers. Further suitable formaldehyde copolymers for the process according to the invention are copolymers of formaldehyde and of trioxane with cyclic and / or linear formals, such as butanediol formal, or epoxides. It is also conceivable that higher homologous aldehydes, such as, for example, acetaldehyde, propionaldehyde, etc., are incorporated into the formaldehyde polymer as comonomers. It is likewise conceivable that formaldehyde starter compounds according to the invention are again prepared starting from H-functional starter compounds; in particular, polymeric formaldehyde starter compounds having a hydroxy end group functionality F> 2 can be obtained by the use of polyvalent starter compounds (cf., for example, WO 1981001712 Al, Bull. Chem. Soc. J., 1994, 67, 2560-2566, US 3436375, JP 03263454, JP 2928823). _r

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Mixtures of different polymeric formaldehyde starter compounds or mixtures with other H-functional starter compounds can also be used for the process according to the invention. As a suitable H-functional starter substance ("starter") can be used compounds having active for the alkoxylation H atoms having a molecular weight of 18 to 4500 g / mol, preferably from 62 to 2500 g / mol and particularly preferably from 62 to 1000 For the alkoxylation, active groups having active H atoms are, for example, -OH, -NH 2 (primary amines), -NH- (secondary amines), -SH and -CO 2 H, preferred are -OH and -NH 2, especially The H-functional starter substance is, for example, one or more compounds selected from the group consisting of mono- or polyhydric alcohols, polyhydric amines, polyhydric thiols, amino alcohols, thioalcohols, hydroxyesters, polyetherpolyols, polyesterpolyols, polyesteretherpolyols, polyethercarbonatepolyols, polycarbonatepolyols, polycarbonates, polyethyleneimines, polyetheramines, polytetrahydrofurans (z. B. PolyTHF ^® of BASF), Polytetrahydrofuranamine, Polyetherthiole, polyacrylate polyols, Ricinus oil, the mono- or diglyceride of ricinoleic acid, monoglycerides of fatty acids, chemically modified mono-, di- and / or triglycerides of fatty acids, and C1-C24 alkyl fatty acid esters containing on average at least 2 OH groups per molecule.

As is known, formaldehyde already polymerizes by the presence of small traces of water. In aqueous solution, therefore, depending on the concentration and temperature of the solution, a mixture of oligomers and polymers of different chain lengths forms, which are in equilibrium with molecular formaldehyde and formaldehyde hydrate. So-called paraformaldehyde in this case precipitates out of the solution as a white, poorly soluble solid and is generally a mixture of linear formaldehyde polymers with n = 8 to 100 oxymethylene repeat units.

An advantage of the method according to the invention is in particular that polymeric formaldehyde or so-called paraformaldehyde, which is commercially available and inexpensive, can be used directly as a starter compound, without the need for additional preparatory steps. In an advantageous embodiment of the invention, paraformaldehyde is therefore used as starter compound. In particular, polyoxymethylene B curls having a defined molecular weight and functionality can be introduced into the product via the molecular weight and end-group functionality of the polymeric formaldehyde starter compound.

Advantageously, in the process according to the invention, the length of the polyoxymethylene block can be controlled simply by the molecular weight of the formaldehyde starter compound used. Preferably, in this case linear formaldehyde starter compounds of the general formula HO- (CH ₂ 0) _n -H, where n is an integer> 2, preferably with n = 2 to 1000, more preferably n = 2 to 400 and very particularly preferably with n = 8 to 100, with used two terminal hydroxyl groups. In particular, mixtures of polymeric formaldehyde compounds of the formula HO- (CH 2 O) _n -H, each having different values of n, can also be used as starter compound. In an advantageous embodiment, the mixtures used of polymeric formaldehyde starter compounds of the formula HO- (CH 2 O) n H contain at least 1% by weight, preferably at least 5% by weight and particularly preferably at least 10% by weight of polymeric formaldehyde compounds with n > 20.

In particular, polyoxymethylene block copolymers having an ABA block structure comprising an inner polyoxymethylene block (B) and outer oligomeric blocks (A) can be obtained by the method of the present invention. It is also possible according to the invention to use formaldehyde starter compounds having a hydroxyl end group functionality F> 2, which therefore have homologous block structures B (-A) _y with a number y> 2 of outer oligomeric blocks (A) corresponding to resulting from the functionality of the formaldehyde starter compound used, can represent. Likewise, it is in principle possible that formaldehyde starter compounds having a functionality F <2 are used; these may, for example, also be linear formaldehyde starter compounds having F = 1 which are substituted at one chain end with a protective group or by other chemical radicals.

A polyoxymethylene block in the meaning of the invention denotes a polymeric structural unit - (CH 2 -) - _x wherein x is an integer> 2, which contains at least one CFh group bound to two oxygen atoms, which contains at least one of the oxygen atoms Methylene groups or other polymeric structures is connected. Polyoxymethylene blocks preferably contain - (CH 2 O-) _x on average x> 2 to x <1000, more preferably on average x> 2 to x <400 and particularly preferably on average x> 8 to x <100 oxymethylene units. For the purposes of the invention, a polyoxymethylene block is also understood as meaning those blocks which contain small amounts of further monomeric and / or oligomeric units, generally less than 25 mol%, based on the total amount of monomer units present in the block.

The outer oligomeric blocks (A) preferably represent polyoxyalkylene or polyoxyalkylene carbonate blocks, and polyoxyalkylene or polyoxyalkylene carbonate blocks within the meaning of the invention are also understood as meaning those blocks in which (small) fractions of further comonomers, generally less than 50 mol -%, preferably less than 25 mol%, based on the total amount of all repeating units present in the oligomeric block, are polymerized.

A polyoxyalkylene carbonate block in the context of the invention denotes a polymeric structural unit -O [(C ₂ R ¹ R ² R ³ R ⁴ O) _x (CO ₂ ) (C ₂ R ¹ R ² R ³ R ⁴ O) _y ] _z -, with x> 1, y> 0 and z> 1, where R ¹ , R ² , R ³ and R ⁴ independently of one another are hydrogen, an optionally additional heteroatom such as nitrogen, oxygen, silicon, sulfur or phosphorus containing alkyl or aryl radical and may differ in different repeating units. The term "alkyl" generally in the context of the entire invention comprises substituents from the group n-alkyl such as methyl, ethyl or propyl, branched alkyl and / or cycloalkyl. The term "aryl" generally in the context of the entire invention substituents from the group mononuclear carbo- or heteroaryl substituents such as phenyl and / or polynuclear carbo- or heteroaryl substituents, optionally with other alkyl groups and / or heteroatoms such as nitrogen, oxygen, silicon, sulfur or Phosphorus may be substituted. The radicals R ^1, R ^2, R ³ and / or R ⁴ may be linked within a repeating unit together so that they form cyclic structures, such as a cycloalkyl residue, which is installed on two adjacent carbon atoms in the polymer chain.

It can be obtained by the inventive method starting from formaldehyde starter compounds which are present as a mixture of different polymer chain lengths, such as paraformaldehyde, polyoxymethylene copolymers having a low content of by-products and decomposition products and a narrow molecular weight distribution. Without wishing to be bound by any particular theory, it is to be assumed that conditioning of the formaldehyde initiator compound also takes place during the activation step of the DMC catalyst, formation of by-products and decomposition products (such as formates, methoxy derivatives, monomeric formaldehyde). , as well as the defragmentation of the polymeric formaldehyde to shorter chain lengths prevented and at the same time a sufficient activity and selectivity of the catalyst is achieved. Here, the formaldehyde starter compound, which is present in thermally and chemically labile and mostly insoluble hemiacetal form is converted by the reaction with the alkylene oxide in a thermally and chemically stable form. Surprisingly, the step of activating the DMC catalyst can be combined with the conditioning of the polymeric formaldehyde initiator and perform particularly advantageous at unexpectedly mild temperatures. The same was not to be expected since DMC catalysts typically require much higher temperatures, for example of 130 ° C, for activation. The conditioning of the formaldehyde starter compound in the presence of the DMC catalyst allows the initiator in the subsequent polymerization step can be reacted at higher reaction temperatures with alkylene oxides and optionally further comonomers, without causing further defragmentation and / or the formation of By-products and decomposition products. Another advantage is that the conditioned formaldehyde starter compound usually has a much higher solubility after conditioning, so that only small amounts or no further solvents and / or suspending agents are needed. Furthermore, it can be ensured by the inventive method that an active DMC catalyst system for the polymerization is present and a steadily progressing polymerization with continuous addition of the comonomers ensures a safe process and high product quality. According to the invention, the activation of the DMC catalyst therefore takes place in the presence of the polymeric formaldehyde starter compound. The initiator compound and the DMC catalyst may optionally be suspended in a suspending agent. Likewise, it is also possible to use a further liquid starter compound ("co-tarter") in the mixture, wherein the DMC catalyst and the polymeric formaldehyde starter compound are suspended in the latter The activation of the DMC catalyst takes place according to the invention at an activation temperature Tact in the region of 20 to 120 ° C, preferably at 30 to 120 ° C, more preferably at 40 to 100 ° C and most preferably at 60 to 100 ° C.

"Activation" of the DMC catalyst is understood to mean a step in which a portion of alkylene oxide is added to the DMC catalyst suspension at the specific activation temperature and then the addition of the alkylene oxide is interrupted, resulting in heat generation due to a subsequent exothermic chemical reaction, which can lead to a temperature peak ("hotspot"), and due to the reaction of alkylene oxide, a pressure drop is observed in the reactor.

DMC catalysts suitable for use in the homopolymerization of alkylene oxides are known in principle from the prior art (see, for example, US Pat. A 5 158 922). DMC catalysts, e.g. in US Pat. No. 5,470,813, EP-A 700 949, EP-A 743 093, EP-A 761 708, WO 97/40086, WO 98/16310 and WO 00/47649 have very high activity in the Polymerization of alkylene oxides and optionally the copolymerization of alkylene oxides with suitable comonomers and allow the preparation of polyoxymethylene copolymers at very low catalyst concentrations, so that a separation of the catalyst from the finished product i. a. is no longer necessary. A typical example is the highly active DMC catalysts described in EP-A 700 949 which, in addition to a double metal cyanide compound (eg zinc hexacyanocobaltate (III)) and an organic complex ligand (eg tert.-butanol), have a polyether with a number average molecular weight greater than 500 g / mol.

The concentration of DMC catalyst used is 10 to 10,000 ppm, more preferably 20 to 5,000 ppm, and most preferably 50 to 2,000 ppm, based on the mass of the produced polyoxymethylene block copolymer. Depending on the requirement profile of the downstream application, the DMC catalyst may be left in the product or (partially) be separated. The (partial) separation of the DMC catalyst can be carried out, for example, by treatment with adsorbents and / or filtration. Methods for the separation of DMC catalysts are described, for example, in US-A-4,987,271, DE-A-3132258, EP-A-0 406 440, US-A-5,391,722, US-A-5,099,075, US-A-4,721,818, US -A-4,877,906 and EP-A-0 385 619.

The epoxide (alkylene oxide) used for the preparation of the polyoxymethylene block copolymers are compounds of the general formula (I):

used, wherein R ¹ , R ² , R ³ and R ^{4 are} independently hydrogen or an optionally additional heteroatoms such as nitrogen, oxygen, silicon, sulfur or phosphorus-containing alkyl or aryl radical and may optionally be linked together such that they form cyclic structures, such as a cycloalkylene oxide.

In the context of the process according to the invention, it is possible in principle to use those alkylene oxides which are suitable for the polymerization in the presence of a DMC catalyst. If different alkylene oxides are used, they can be added either as a mixture or in succession. In the case of the latter metering method, the polyether chains of the polyoxymethylene-polyoxyalkylene block copolymer obtained therefrom can likewise have a block structure.

In general, alkylene oxides (epoxides) having 2-24 carbon atoms can be used for the process according to the invention. The alkylene oxides having 2-24 carbon atoms are, for example, one or more compounds selected from the group consisting of ethylene oxide, propylene oxide, 1-butene oxide, 2,3-butene oxide, 2-methyl-1,2-propene oxide (isobutene oxide), 1-pentoxide, 2,3-pentenoxide, 2-methyl-l, 2-butene oxide, 3-methyl-1,2-butene oxide, 1-hexene oxide, 2,3-hexene oxide, 3,4-hexene oxide, 2-methyl- 1, 2-pentenoxide, 4-methyl-l, 2-pentenoxide, 2-ethyl-l, 2-butene oxide, 1-epoxide, 1-octene oxide, 1-nonene oxide, 1-decene oxide, 1-undecenoxide, 1-dodecene oxide, 4-methyl-l, 2-pentenoxide, butadiene monoxide, isoprene monoxide, cyclopentene oxide, cyclohexene oxide, cycloheptenoxide, cyclooctene oxide, styrene oxide, methylstyrene oxide, pinene oxide, mono- or poly-epoxidized fats as mono-, di- and triglycerides, epoxidized fatty acids, C1-C24- Esters of epoxidized fatty acids, epichlorohydrin, glycidol, and derivatives of glycidol such as methyl glycidyl ether, ethyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl eth he, glycidyl methacrylate and epoxy-functional alkyoxysilanes such For example, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltripropoxysilane, 3-glycidyloxypropyl-methyl-dimethoxysilane, 3-glycidyloxypropyl-ethyldiethoxysilane, 3-glycidyloxypropyltrlisopropoxysilane. Preferably, the epoxide of the general formula (I) is a terminal epoxide, wherein R ¹ , R ² and R ^{3 are} hydrogen, and R ^{4 is} hydrogen, an optionally additional heteroatoms such as nitrogen, oxygen, silicon, sulfur or phosphorus-containing alkyl or Aryl may be and may differ in different repeating units. The alkylene oxides used are preferably ethylene oxide and / or propylene oxide, in particular propylene oxide.

The process according to the invention is preferably carried out in such a way that the activation of the catalyst and the conditioning of the polymeric formaldehyde initiator compound in step (β) are followed by a polymerization step (γ) with metered addition of one or more alkylene oxides. In principle, however, the process can also be terminated after step (β), so that the conditioned polymeric formaldehyde starter compound is then the end product of the process. This generally has a high stability by the conditioning according to the invention and, analogously to the polyoxymethylene block copolymer obtained from step (γ), if desired, can be used as an OH-functional building block for various subsequent reactions.

In a further embodiment of the process according to the invention, the polymerization of the alkylene oxides takes place in the presence of a further comonomer. As further comonomers, for example, all oxygen-containing cyclic compounds, in particular cyclic ethers, such as e.g. Oxetane, THF, dioxane or cyclic acetals such as e.g. 1,3-dioxolane or 1,3-dioxepane, cyclic esters such as e.g. γ-butyrolactone, γ-valerolactone, ε-caprolactone, or cyclic acid anhydrides, e.g. Maleic anhydride, glutaric anhydride or phthalic anhydride and carbon dioxide are used. Preferably, carbon dioxide is used as comonomer.

The dosage of other co-monomers can be carried out in pure substance, in solution or as a mixture with one or more alkylene oxides. The dosage of other co-monomers can also be done in parallel with the dosage or following the dosage of the alkylene oxides.

In a preferred embodiment of the process according to the invention, in addition to the addition of the alkylene oxide (s) to the polymeric formaldehyde starter compound, the addition of carbon dioxide (CO2) as further comonomer takes place. Over this can be produced polyoxymethylene-polyoxyalkylene carbonate copolymers. These have in addition to existing products (for example, polyether polyols in the polyurethane sector or polyoxymethylene (co) polymers in the POM sector) in addition to CO2 as a cost-effective and environmentally friendly comonomer. As CO2, inter alia, a waste product of energy "

- 12 - fossil raw materials and is here a renewed chemical recovery, resulting from the incorporation of CO ₂ in the polymer structures in addition to economic and environmental benefits (favorable CC balance of the product polymers, etc.).

Polyoxymethylene-polyoxyalkylene carbonate block copolymers in the context of the invention refer to polymeric compounds which contain at least one polyoxymethylene block and at least one polyoxyalkylene carbonate block. Polyoxymethylene-polyoxyalkylene carbonate block copolymers are of particular interest as feedstocks in the polyurethane sector, as well as for applications in the polyoxymethylene (POM) sector. By changing the CC content, the physical properties can be adapted to the particular application, which opens up new fields of application for these block copolymers. In particular, polyoxymethylene-polyoxyalkylene carbonate copolymers can be provided via the process according to the invention, a high content of incorporated CO _{2 being} achieved, the products having a comparatively low polydispersity and containing very few by-products and decomposition products of the polymeric formaldehyde. European Patent Application EP13171772.0 discloses a process for the preparation of polyoxyalkylene carbonate-polyoxymethylene block copolymers wherein polyoxyalkylene carbonates having Zerewitinoff-active H atoms are reacted as starter compounds with gaseous monomeric formaldehyde being polymerized. However, polyoxymethylene-polyoxyalkylene carbonate block copolymers having internal polyoxymethylene blocks can not be built by this process, and the products obtained from the polymerization with monomeric formaldehyde must be reacted in an additional step with epoxides, cyclic carboxylic or carbonic acid esters to form stable products with terminal functionalities to obtain.

Several variants for carrying out the process according to the invention for the preparation of polyoxymethylene block copolymers by addition of alkylene oxides and optionally further comonomers to polymeric formaldehyde starter compounds are described in detail below. The illustration is merely exemplary and not to be construed as limiting the present invention.

For example, the method according to the invention is characterized in that in the first step (i)

(a) a suspension agent or a polymeric formaldehyde starter compound is initially charged and optionally water and / or other readily volatile compounds are removed by increased temperature and / or reduced pressure ("drying"), the DMC Catalyst is added to the polymeric formaldehyde starter compound or the suspending agent before or after drying,

(β) for activating the DMC catalyst in the presence of the polymeric formaldehyde starter compound, a partial amount (based on the total amount of used in the activation and polymerization amount of alkylene oxides) of one or more

Alkylene oxides are added to the mixture resulting from step (a), wherein this addition of a partial amount of alkylene oxide may optionally be carried out in the presence of further comonomers, such as in particular CO2, and then occurring due to the following exothermic chemical reaction temperature peak ("hotspot" ) and / or a pressure drop in the reactor is respectively awaited, and wherein the step (ß) for

Activation can also take place several times, and in the second step (ii)

(γ) one or more alkylene oxides and optionally further comonomers, in particular carbon dioxide, are added to the mixture resulting from step (β), wherein the alkylene oxides used in step (γ) may be the same or different from those of

Step (ß) alkylene oxides used ("polymerization"), wherein at least one of the steps in step (a) and (ß) at least one polymeric formaldehyde starter compound is added.

The polymeric formaldehyde starter compound may in this case be introduced together with the DMC catalyst and the suspending agent in step (a), or preferably after drying, at the latest in step (β).

The suspending agents optionally used generally contain no H-functional groups. Suitable suspending agents are all polar aprotic, weakly polar aprotic and nonpolar aprotic solvents, each of which is not H-functional

Contain groups. As suspending agent, it is also possible to use a mixture of two or more of these suspending agents. By way of example, the following polar aprotic suspending agents may be mentioned at this point: 4-methyl-2-oxo-1,3-dioxolane (also referred to below as cyclic propylene carbonate or cPC), 1,3-dioxolan-2-one (hereinafter also as cyclic ethylene carbonate or cEC), acetone, methyl ethyl ketone, acetonitrile, nitromethane,

Dimethylsulfoxide, sulfolane, dimethylformamide, dimethylacetamide and N-methylpyrrolidone. For example, ethers such as dioxane, diethyl ether, methyl tert-butyl ether and tetrahydrofuran, esters such as _Λ

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Ethyl acetate and butyl acetate, hydrocarbons, e.g. Pentane, n-hexane, benzene and alkylated benzene derivatives (e.g., toluene, xylene, ethylbenzene) and chlorinated hydrocarbons such as, chloroform, chlorobenzene, dichlorobenzene and carbon tetrachloride. Preferred suspending agents are 4-methyl-2-oxo-1,3-dioxolane, 1,3-dioxolan-2-one, toluene, xylene, ethylbenzene, chlorobenzene and dichlorobenzene, and mixtures of two or more of these suspending agents, more preferably 4 Methyl 2-oxo-1,3-dioxolane and 1,3-dioxolan-2-one and toluene or a mixture of 4-methyl-2-oxo-1,3-dioxolane and 1,3-dioxolane-2 on and / or toluene. It is also possible as suspending agent to use a further starter compound which is in liquid form under the reaction conditions in admixture with the polymeric formaldehyde starter compound.

To step (et): (drying)

The addition of the individual components in step (a) can take place simultaneously or successively in any order.

In step (a), preference is given to initially charging a suspending agent which does not contain any H-functional groups in the reactor. Subsequently, the amount of DMC catalyst required for the polymerization, which is preferably not activated, is added to the reactor. The order of addition is not critical. It is also possible first to fill the DMC catalyst and then the suspending agent into the reactor. Alternatively, it is also possible for the DMC catalyst to be suspended in the suspending agent first and then the suspension to be filled into the reactor. By means of the suspending agent, a sufficient heat exchange surface with the reactor wall or cooling elements installed in the reactor is made available, so that the released heat of reaction can be dissipated very well. In addition, the suspension agent provides heat capacity in the event of a cooling failure, so that the temperature in this case can be kept below the decomposition temperature of the reaction mixture. Alternatively, in step (a) a suspension agent containing no H-functional groups, and additionally a portion of the polymeric formaldehyde starter compound and optionally DMC catalyst may be presented in the reactor, or it may also in step (a) a subset of polymeric formaldehyde starter compound and optionally DMC catalyst are introduced into the reactor. Furthermore, in step (a), the total amount of the polymeric formaldehyde starter compound and optionally DMC catalyst can be initially charged in the reactor.

The polymeric formaldehyde starter compound can in principle be presented as a mixture with further polymeric formaldehyde starter compounds or other H-functional starter compounds. The process may be carried out by initially introducing in step (a) a suspending agent, the polymeric formaldehyde initiator compound and the DMC catalyst, and optionally removing water and / or other volatile compounds by elevated temperature and / or reduced pressure (" Drying ") or in an alternative embodiment, the step (a) is carried out such that in a step (al) a suspending agent and the DMC catalyst and optionally water and / or other volatile compounds by increased temperature and / or reduced pressure are removed ("drying") and in a subsequent step (a2) to the mixture of step (al), the formaldehyde-initiator compound is added. The addition of the polymeric formaldehyde starter compound can be carried out after cooling the reaction mixture from step (a1), in particular at room temperature, or the reaction mixture can already be brought to the temperature prevailing in the subsequent step (.beta.) And the addition carried out at this temperature. The addition of the formaldehyde starter compound is generally carried out under inert conditions. The DMC catalyst is preferably used in an amount such that the content of DMC catalyst in the resulting reaction product is 10 to 10,000 ppm, more preferably 20 to 5,000 ppm, and most preferably 50 to 2,000 ppm.

In a preferred embodiment, in the resulting mixture of suspending agent and DMC catalyst and / or the polymeric formaldehyde starter compound at a temperature of 90 to 150 ° C, more preferably from 100 to 140 ° C inert gas (for example, argon or nitrogen), a Inert gas-carbon dioxide mixture or carbon dioxide introduced while a reduced pressure (absolute) of 10 mbar to 800 mbar, more preferably from 50 mbar to 200 mbar applied.

In an alternative preferred embodiment, the resulting mixture of DMC catalyst with suspending agent and / or the polymeric formaldehyde starter compound at a temperature of 90 to 150 ° C, more preferably from 100 to 140 ° C at least once, preferably three times with 1 bar 100 bar (absolute), more preferably 3 bar to 50 bar (absolute) of an inert gas (for example, argon or nitrogen), an inert gas-carbon dioxide mixture or carbon dioxide applied and then the overpressure to about 1 bar to 20 bar (absolute) reduced.

The DMC catalyst can be added, for example, in solid form or as a suspension in one or more suspension media or, if the polymeric formaldehyde starter compound is in a liquid state, as a suspension in a polymeric formaldehyde initiator compound. To step (ß): (Activation)

Step (β) serves to activate the DMC catalyst. This step may optionally be carried out under an inert gas atmosphere, under an inert gas-carbon dioxide mixture atmosphere or under a carbon dioxide atmosphere. Activation for the purposes of this invention is a step in which a portion of alkylene oxide at temperatures of 20 to 120 ° C ("activation temperature") is added to the DMC catalyst suspension and then the addition of the alkylene oxide is interrupted, due to a following exothermal chemical reaction heat generation, which can lead to a temperature spike ("hotspot"), as well as due to the reaction of alkylene oxide and optionally CO2 a pressure drop is observed in the reactor.

In a preferred embodiment, the amount of one or more alkylene oxides used in the activation in step (β) is 2 to 100 molar equivalents, preferably 4 to 50 molar equivalents, more preferably 4.5 to 25 molar equivalents based on the molar amount of polymeric formaldehyde starter compound , wherein the number average molecular weight (M _n ) of the formaldehyde starter compound or the mixtures used is based. The alkylene oxide can be added in one step or in stages in several aliquots. Preferably, after the addition of a partial amount of alkylene oxide, the addition of the alkylene oxide is interrupted until the evolution of heat has occurred and only then is the next portion of alkylene oxide added. For the inventive method has further been shown that the activation (step (ß)) in the presence of the polymeric formaldehyde starter compound for the preparation of the polyoxymethylene block copolymers advantageously at an activation temperature T _act of 20 to 120 ° C, preferably at 30 to 120 ° C, more preferably at 40 to 100 ° C and most preferably at 60 to 100 ° C is performed. The heat development by the chemical reaction in the activation of the DMC catalyst according to the invention preferably does not lead to exceeding a temperature of 120 ° C in the reaction vessel. Below 20 ° C, the reaction proceeds only very slowly and activation of the DMC catalyst takes a disproportionately long time or may not take place to the desired extent. At temperatures of 130 ° C and higher, the amount of undesirable side / decomposition products of polymeric formaldehyde starter compounds increases sharply. For example, the formation of formate and methoxy traces is observed. It has further been found to be an advantage of this embodiment that the properties of the obtained polyoxymethylene block copolymer, in particular the length of the polyoxymethylene block, can also be influenced by precise matching of the parameters in this range. - 17 -

The step of activation is the period from the addition of the subset of alkylene oxide, optionally in the presence of CO2, to the reaction mixture comprising a suspending agent, DMC catalyst and the formaldehyde starter compound until the evolution of heat (exotherm) occurs. If appropriate, the partial amount of the alkylene oxide can be added to the reaction mixture in several individual steps, if appropriate in the presence of CO ₂ , and the addition of the alkylene oxide can then be interrupted in each case. In this case, the activation step comprises the period from the addition of the first aliquot of alkylene oxide, optionally in the presence of CO 2, to the reaction mixture until the evolution of heat after the addition of the last aliquot of alkylene oxide has occurred. In general, the activating step may be preceded by a step of drying the DMC catalyst and optionally the polymeric formaldehyde initiator compound at elevated temperature and / or reduced pressure, optionally passing an inert gas through the reaction mixture, which drying step is not part of the reaction Activation step in the context of the present invention. The metering of one or more alkylene oxides (and optionally the further comonomers, in particular carbon dioxide) can in principle be carried out in different ways. The start of dosing can be carried out from the negative pressure or at a previously selected form. The admission pressure is preferably set by introducing an inert gas (such as nitrogen or argon) or carbon dioxide, the pressure being (absolute) 5 mbar to 100 bar, preferably 10 mbar to 50 bar and preferably 20 mbar to 50 bar.

An alternative embodiment is also a two-stage activation (step β), wherein

(β-I) in a first activation stage, the addition of a first subset of alkylene oxide takes place under an inert gas atmosphere, and

(β-II) in a second activation stage, the addition of a second subset of alkylene oxide takes place under a carbon dioxide atmosphere, wherein the polymeric formaldehyde starter compound before and after substep (□ DI) can be added.

To step (γ): (polymerization)

The dosage of one or more alkylene oxides can be carried out simultaneously or sequentially via separate dosages (additions) or via one or more dosages. If several alkylene oxides are used for the synthesis of the polyoxymethylene block copolymers, the alkylene oxides can be metered individually or as a mixture. For the process according to the invention, it has been found that the polymerization for preparing the polyether block in the polyoxymethylene-polyoxyalkylene block copolymers (step (□)) is advantageously at 50 to 150 ° C., preferably at 60 to 145 ° C., particularly preferably at 70 to 140 ° C and most preferably at 90 to 130 ° C is performed. If temperatures below 50 ° C are set, the reaction proceeds disproportionately slowly. At temperatures above 150 ° C, the amount of unwanted by-products increases sharply.

In a further embodiment of the process according to the invention, the polymerization is carried out in the presence of at least one comonomer. The dosage of the other comonomers can be carried out in pure substance, in solution or else in any technically realizable forms. The dosage of one or more alkylene oxides and the co-monomers may be simultaneous or sequential, wherein the total amount of co-monomer may be added all at once or metered over the reaction time. In a preferred embodiment of the invention, carbon dioxide is metered in as comonomer. The metering of one or more alkylene oxides takes place simultaneously or sequentially to the carbon dioxide metering. By way of the manner of metering the alkylene oxides and the comonomers, preferably carbon dioxide, it is possible to synthesize polyoxymethylene block copolymers with random, alternating, block-like or gradient-like polyether and / or polyoxyalkylene carbonate blocks.

In the preparation of the polyoxymethylene-polyoxyalkylene carbonate block copolymers copolymerizing CO2 as a comonomer, an excess of carbon dioxide is preferably used based on the expected or estimated amount of incorporated carbon dioxide in the polyoxyalkylene carbonate block, since an excess of carbon dioxide is advantageous due to the inertness of carbon dioxide is. The amount of carbon dioxide can be set by the total pressure at the respective reaction conditions. As total pressure (absolute), the range of 0.01 to 120 bar, preferably 0.1 to 110 bar, more preferably from 1 to 100 bar for the copolymerization for the preparation of the Polyoxyalkylencarbonatblockes has proven to be advantageous. For the process according to the invention, it has furthermore been found that the copolymerization for the preparation of the polyoxyalkylene carbonate block is advantageously at 50 to 150.degree. C., preferably at 60 to 145.degree. C., particularly preferably at 70 to 140.degree. C. and very particularly preferably at 90 to 130.degree is carried out. If temperatures below 50 ° C are set, the reaction proceeds disproportionately slowly. At temperatures above 150 ° C, the amount of unwanted by-products increases sharply. Furthermore, it should be noted that the CO ₂ passes in the choice of pressure and temperature from the gaseous state as possible in the liquid and / or supercritical fluid state. However, CO ₂ may also be added to the reactor as a solid and then converted to the liquid and / or supercritical fluid state under the chosen reaction conditions. Carbon dioxide can be used in gaseous, solid, liquid or supercritical state, preferably in gaseous or solid, more preferably in the gaseous state. When using carbon dioxide in the gaseous state, a carbon dioxide partial pressure of 1 to 73.8 bar, preferably from 1 to 60 bar, more preferably selected from 5 to 50 bar. The combination of pressure and temperature is selected when using gaseous carbon dioxide such that carbon dioxide is in the gaseous state as a pure substance under the selected reaction conditions. The corresponding conditions can be derived from the phase diagram. After introducing gaseous carbon dioxide into the reactor, this partially or completely dissolves in the reaction mixture. The three steps (a), (β) and (γ) can be carried out in the same reactor or separately in different reactors. Particularly preferred reactor types for the process according to the invention are stirred tank, tubular reactor, and loop reactor. Furthermore, extruders, kneaders, etc. can also be used as preferred reactors for the process according to the invention. If the reaction steps α, β and γ are carried out in different reactors, a different type of reactor can be used for each step. In the case of a completely continuous reaction procedure, the individual steps or steps (a) and (β) of (γ) are preferably spatially separated from one another, so that a separate temperature control and a suitable gas supply and application of reduced pressure, addition of polymeric formaldehyde and metering of monomers in the individual steps according to the invention is possible.

On account of their thermal and chemical stability, the polyoxymethylene block copolymers according to the invention or the product mixtures obtained from the process can be worked up, in particular by distillation. In this case, preference is given to using thin-film evaporators, strand evaporators and stripping columns, and combinations of these for removing solvents or suspending agents, volatile constituents and unreacted monomers and / or oligomers. However, in principle all other apparatuses for thermal distillative workup are also suitable here. This type of workup can be carried out continuously or discontinuously as well as in parallel or following the reaction.

Another object of the present invention are polyoxymethylene block copolymers, obtainable by the inventive method.

In particular, the molecular weight of the polyoxymethylene block copolymers according to the invention results additively from the molecular weight of the polymeric formaldehyde starter compound and the grafted-on blocks. In one embodiment, the polyoxymethylene block copolymers have a number average molecular weight of <15,000 g / mol, preferably <9500 g / mol, more preferably <6000 g / mol, very particularly preferably <5000 g / mol, in particular from 200 g / mol to 9500 g / mol, preferably from 500 g / mol to 5000 g / mol. The number average molecular weight can be determined, for example, by gel permeation chromatography (GPC) against, for example, polystyrene standards and / or experimentally determined hydroxyl numbers (OH #). The polyoxymethylene block copolymers obtainable by the process according to the invention have a block structure comprising an internal polyoxymethylene block (B) comprising at least two and at most 1000 oxymethylene units, preferably at least 2 and at most 400 oxymethylene units, more preferably from 8 to 200, and most preferably at least 8 and at most 100 Oxymethylenemheiten, and at least one outer oligomeric block (A), which preferably comprises a proportion of at least 25 mol%, particularly preferably at least 50 mol% of polyoxyalkylene units, based on the total amount of all oligomer units in this block. The number of outer oligomeric blocks (A) results accordingly from the functionality of the formaldehyde starter compound used. Preferably, the polyoxymethylene-polyoxyalkylene block copolymer consists exclusively of blocks A and B. In an advantageous embodiment, the outer oligomeric block is a polyoxyalkylene block, more preferably a polyoxyalkylene carbonate block.

The polyoxymethylene block copolymers according to the invention preferably have terminal hydroxy groups and preferably have a functionality F> 2 (number of hydroxyl groups per molecule). In a further embodiment of the polyoxymethylene block copolymers, these have a monomodal molecular weight distribution and a polydispersity index (PDI) of <2.5, preferably <2.2.

The polyoxymethylene block copolymers obtainable by the process according to the invention preferably contain less than 2% by weight, in particular less than 1% by weight, based on the total mass of the resulting polyoxymethylene block copolymer, formate and / or methoxy impurities.

The invention likewise provides a polyoxymethylene-polyoxyalkylene carbonate block copolymer comprising an inner polyoxymethylene block ("starter") and at least one outer polyoxyalkylene carbonate block of the formula (II)

(Π) wherein R is an organic radical such as alkyl, alkylaryl, arylalkyl or aryl, which may each contain heteroatoms such as O, S, Si, etc., and wherein a, b, and c are an integer number and R are in different And wherein the structural unit "starter" represents a polyoxymethylene block resulting from the polymeric formaldehyde starter compound, and wherein the product for the polyoxymethylene-polyoxyalkylene carbonate block copolymer shown here in the formula (II) is to be understood merely as that blocks having the structure shown can in principle be found in the obtained polyoxymethylene-polyoxyalkylene carbonate block copolymer, but the order, number and length of the blocks and the OH functionality of the "starter" can vary and not to that shown in scheme (II) Polyoxymethylene polyoxyalkylene carbonate block copolymer is limited.

The obtainable by the process according to the invention polyoxymethylene block copolymers generally have a low content of by-products and decomposition products, such as formate, methoxy, monomeric and oligomeric formaldehyde, residual monomers and can be easily processed, in particular by reaction with di-, tri and or polyisocyanates to polyurethanes, isocyanate-functionalized polyurethane prepolymers or polyisocyanurates, in particular polyurethane thermoplastics, polyurethane coatings, fibers, elastomers, adhesives and in particular also polyurethane foams including soft (such as polyurethane soft block foams and polyurethane Soft foam) and rigid foams. For polyurethane applications, polyoxymethylene block copolymers having a functionality of at least 2 are preferably used. In addition, the polyoxymethylene block copolymers obtainable by the process according to the invention can be used in applications such as washing and cleaning agent formulations, adhesives, paints, varnishes, functional fluids, drilling fluids, fuel additives, ionic and nonionic surfactants, lubricants, process chemicals for the paper or textile production or cosmetic / medical formulations are used. It is known to the person skilled in the art that, depending on the particular field of application, the polymers to be used have to fulfill certain material properties such as molecular weight, viscosity, polydispersity, functionality and / or hydroxyl number (number of terminal hydroxyl groups per molecule).

The invention therefore also relates to the use of polyoxymethylene block copolymers according to the invention for the preparation of polyurethane polymers. In one embodiment of this ""

- 22 -

Use are the polyurethane polymers polyurethane foams or rigid polyurethane foams. In a further embodiment of this use, the polyurethane polymers are thermoplastic polyurethane polymers.

The invention therefore likewise provides a polyurethane polymer obtainable by reacting a di-, tri- and / or polyisocyanate with at least one polyoxymethylene block copolymer according to the invention.

The invention likewise provides a flexible polyurethane foam or a rigid polyurethane foam obtainable by reacting a di-, tri- and / or polyisocyanate with at least one polyoxymethylene block copolymer according to the invention.

The invention also includes the use of polyoxymethylene block copolymers according to the present invention for the preparation of polyurethanes, washing and cleaning agent formulations, drilling fluids, fuel additives, ionic and nonionic surfactants, lubricants, process chemicals for the paper or textile production or cosmetic formulations.

Examples

Used connections:

Paraformaldehyde from Ineos was used. Propylene oxide was purchased from Sigma-Aldrich and used without purification. As DMC catalyst DMC catalyst was prepared in all examples according to Example 6 in WO 01/80994 Al, containing

Zinkhexacyanocobaltat, tert-butanol and polypropylene glycol having a number average molecular weight of 1000 g / mol used.

Example 1: Preparation of a polyoxymethylene-polyoxyalkylene carbonate block copolymer In a 300 mL pressure reactor with gas and Flüssigkeitsdosierungseinrichtung 65 mg of unactivated DMC catalyst were suspended in 30 g of toluene. The suspension was heated with stirring to 130 ° C, 40 bar N ₂ pressed and then the N ₂ pressure lowered to 15 bar. The pressing and discharging of N ₂ was carried out twice in the same manner. The suspension thus obtained was cooled to room temperature and the N ₂ pressure was released. The pressure reactor was then opened and 15 g of paraformaldehyde (pFA) added to the present suspension. After the reactor was closed and heated to 40 ° C. (T _act ) with stirring (1200 rpm), 15 g of propylene oxide (PO) were added at a metering rate of 10 g / min. The beginning of the reaction was noticeable by a pressure drop to the initial pressure and a slight increase in temperature. After activation, at a temperature of 100 ° C and 50 bar carbon dioxide (CO2), 75 g of PO was added continuously at a rate of 1 g / min and with stirring (1200 rpm). The progress of the reaction was observed by means of CO ₂ consumption, the pressure being kept constant at 50 bar in the reactor by continuous addition of the feed. After completion of the PO addition was stirred at 100 ° C and reaction pressure for 2 h (1200 U / min). It was then cooled to room temperature. The reaction mixture was analyzed by NMR and GPC analysis, and the results are shown in Table 1.

The composition of the polymer was determined by means of 1 H-NMR (Broker, DPX 400, 400 MHz, pulse program zg30, waiting time DI: 10 s, 64 scans). Each sample was dissolved in deuterated chloroform. The relevant resonances in 'H-NMR (relative to TMS = 0 ppm) and the assignment of the surface integrals (A) are as follows:

• cyclic propylene carbonate (cPC), by-product, with resonance at 4.5 ppm, area integral corresponds to one H atom; • linear propylene carbonate in the polymer (IPC) with resonances at 1.2 to 1.4 ppm, area integral minus 3 H atoms of the monomeric propylene oxide (PO) thus corresponds to 3 H atoms;

• monomeric propylene oxide (PO), which is not fully reacted, with resonance at 2.4 and 2.75 ppm, area integral corresponds to one H atom;

• polypropylene oxide (PPO), PO homopolymer, with resonances at 1.0 to 1.2 ppm, area integral corresponds to 3 H atoms;

• Poly- or paraformaldehyde (pFA) with resonances at 4.6 to 5.2 ppm, area integral minus one H-atom of the cyclic propylene carbonate (cPC) and the linear propylene carbonate (IPC) thus corresponds to 2 H atoms;

• Formate (HCOO), by-product, with resonance at 8.1 ppm, area integral corresponds to one H atom;

• Methoxy (MeO), byproduct in trace amounts, with resonance at 3.4 ppm. The determination of the mole fractions (x) of the reaction mixture is carried out as follows: x (cPC) = A (4.5 ppm)

• x (lPC) = A (1, 2-1, 4 ppm) - (3 x (PO))

• x (PO) = A (2.75 ppm) or A (2.4 ppm)

• x (PPO) = A (l, 0-l, 2 ppm) / 3

• x (pFA) = (A (4.6-5.2 ppm) - x (cPc) - x (1PC)) / 2 * x (HCOO) = A (8, 1 ppm)

The thus determined composition of the reaction mixture is then converted into parts by weight and normalized to 100. The following molecular weights (g / mol) are used to convert the proportions by weight: cPC and IPC = 102, PO and PPO = 58, pFA = 30 and HCOO = 45. The polymer composition is calculated and normalized by means of the proportions IPC, PPO and pFA that here too, the information in parts by weight of 100 (wt .-%) takes place. The CO2 content of the polymer structure is additionally reported in% by weight: IPC · (44 / (44 + 58)), the factors in each case being the molar masses of CO.sub.2 (molar mass 44 g / mol) and that of propylene oxide (Molecular weight 58 g / mol). ^

The weight and number average molecular weight of the resulting polymers was determined by gel permeation chromatography (GPC). The procedure followed was based on DIN 55672-1: "Gel permeation chromatography, Part 1 - tetrahydrofuran as eluent". In this case, polystyrene samples of known molecular weight were used for calibration.

The molecular weight of the pFA block in the product polymer was calculated according to the following formula:

MW (PFA) = M _n (GPC) · (pFA fraction in the polymer, NMR) / 100, where M _n (GPC) is the determined by GPC number average M _n. The polydispersity PDI is given for the molecular weight distribution M _w / M _n .

Example 2: Preparation of a polyoxymethylene-polyoxyalkylene carbonate block copolymer

According to Example 1, a polyoxymethylene-polyoxyalkylene carbonate polyol was prepared, wherein the temperature of the catalyst activation at 60 ° C (T _act ) was set. The results are shown in Table 1.

Example 3: Preparation of a polyoxymethylene-polyoxyalkylene carbonate block copolymer

According to Example 1, a polyoxymethylene-polyoxyalkylene carbonate polyol was prepared, wherein the temperature of the catalyst activation at 80 ° C (T _act ) was set. The results are shown in Table 1.

Example 4: Preparation of a polyoxymethylene-polyoxyalkylene carbonate block copolymer

A polyoxymethylene-polyoxyalkylene carbonate polyol was prepared according to Example 1 with the catalyst activation temperature set at 100 ° C (Tact). The results are shown in Table 1.

Example 5: Preparation of a Polyoxymethylene-Polyoxyalkylene Carbonate Block Copolymer (Tact = 130 ° C) (Comparative Example)

A polyoxymethylene-polyoxyalkylene carbonate polyol was prepared according to Example 1 with the catalyst activation temperature set at 130 ° C (Tact). The results are shown in Table 1.

Example 6 Preparation of a Polyoxymethylene-Polyoxyalkylene Carbonate Block Copolymer (Tact = 150 ° C) (Comparative Example) According to Example 1, a polyoxymethylene-polyoxyalkylene carbonate polyol was prepared, wherein the temperature of the catalyst activation at 150 ° C (T _act ) was set. The results are shown in Table 1.

Example 7 Preparation of a Polyoxymethylene-Polyoxyalkylene Block Copolymer (T _ac t = 70 ° C)

In a 300 mL pressure reactor with gas and Flüssigkeitsdosierungseinrichtung 65 mg of unactivated DMC catalyst were suspended in 30 g of toluene. The suspension was heated with stirring to 130 ° C, 40 bar N ₂ pressed and then the N ₂ pressure lowered to 15 bar. The pressing and discharging of N ₂ was carried out twice in the same manner. The suspension thus obtained was cooled to room temperature and the N ₂ pressure was released. The pressure reactor was now opened and 15 g of pFA added to the present suspension. After the reactor was closed and heated to 70 ° C. (Tact) with stirring (1200 rpm), the addition of 15 g of PO was carried out at a metering rate of 10 g / min. The beginning of the reaction was noticeable by a pressure drop to the initial pressure and a slight increase in temperature. After the activation was carried out at a temperature of

100 ° C 75 g PO added continuously at a rate of 1 g / min and with stirring (1200 U / min). After completion of the PO addition was stirred at 100 ° C for 2 h (1200 U / min). It was then cooled to room temperature. The reaction mixture was analyzed by NMR and GPC analysis. The results are shown in Table 1. Example 8: Preparation of a polyoxymethylene-polyoxyalkylene carbonate block copolymer

In a 300 mL pressure reactor with gas and Flüssigkeitsdosierungseinrichtung 65 mg of unactivated DMC catalyst in 30 g of cPC (4-methyl-2-oxo-l, 3-dioxolane, cyclic propylene carbonate) were suspended. The suspension was then heated to 130 ° C and over 30 min was introduced with 2.5 L / h of nitrogen and simultaneously applied a reduced pressure of 75-100 mbar. The resulting suspension was cooled to room temperature. The pressure reactor was now opened and 15 g of pFA added to the present suspension. After the reactor was closed and heated with stirring (1200 rpm) to 60 ° C (Tact), the addition of 15 g of PO was carried out at a metering rate of 10 g / min. The beginning of the reaction was noticeable by a pressure drop to the initial pressure and a slight increase in temperature. Subsequently, at a temperature of 100 ° C. and 50 bar of CO2, 75 g of PO were added continuously at a metering rate of 1 g / min and with stirring (1200 rpm). The progress of the reaction was observed by means of CO ₂ consumption, the pressure being kept constant at 50 bar in the reactor by continuous addition of the feed. After completion of PO addition was stirred at 100 ° C and reaction pressure for 2 h (1200 U / min). Subsequently was "

- 27 - cooled to room temperature. The reaction mixture was analyzed by NMR and GPC analysis. The results are shown in Table 1.

Table 1: Results of Polyoxymethylene Block Copolymer Preparation

= Comparative Example, a) in the reaction mixture, b) in the polymer.

Table 1 summarizes the results for the preparation of the polyoxymethylene block copolymers. By means of the process according to the invention, products having a defined polyoxymethylene block (pFA block) and a low polydispersity can be obtained without a decomposition or defragmentation of the paraformaldehyde used as initiator compound being observed in smaller oligomers or monomers. Furthermore, polyoxymethylene-polyoxyalkylene carbonate block copolymers can be obtained by the process according to the invention by copolymerization, almost complete conversions of the alkylene oxide being achieved with simultaneously high CO 2 incorporation rates. Comparative Examples 5 and 6 show that at higher temperatures, which are in the range of usually set activation temperatures for DMC catalysts, defragmentation of the polymeric formaldehyde initiator takes place and secondary products are formed.

Claims

claims

1. A process for the preparation of polyoxymethylene block copolymers by catalytic addition of alkylene oxides and optionally further comonomers to at least one polymeric formaldehyde starter compound having at least one terminal hydroxyl group, in the presence of a double metal cyanide (DMC) - catalyst, wherein

(I) in a first step, the DMC catalyst is activated in the presence of the polymeric formaldehyde starter compound, wherein to activate the DMC catalyst, a partial amount (based on the total amount of used in the activation and polymerization amount of alkylene oxides) of one or more Alkylene oxides are added,

(Ii) in a second step, one or more alkylene oxides and optionally further comonomers are added to the mixture resulting from step (i), wherein the alkylene oxides used in step (ii) may be the same or different from the alkylene oxides used in step (i) , characterized in that the activation of the DMC catalyst in the first step (i) takes place at an activation temperature (T _act ) of 20 to 120 ° C.

2. The process according to claim 1, wherein at least one open-chain polymeric formaldehyde starter compound having n oxymethylene repeating units and a functionality F of 1 to 10, in particular a linear formaldehyde starter compound of the general formula HO- (CH 2 O) _n -H having two terminal hydroxyl groups is used, where n is an integer from n = 2 to 400, in particular from 8 to 100, and wherein the starter compound may in particular also be present as a mixture of polymeric formaldehyde starter compounds each having different values for n.

3. The method according to claim 1 or 2, wherein paraformaldehyde is used as a polymeric formaldehyde starter compound.

4. The method according to any one of the preceding claims, wherein the used in step (i) amount of one or more alkylene oxides is 2 to 100 molar equivalents based on the amount of molar amount of polymeric formaldehyde starter compound.

5. The method according to any one of the preceding claims, wherein in step (ii) carbon dioxide is added as a comonomer.

6. The method according to any one of the preceding claims, wherein in the first step (i)

(A) a suspending agent or the polymeric formaldehyde starter compound and optionally water and / or other volatile compounds are removed by elevated temperature and / or reduced pressure, wherein the DMC catalyst of the polymeric formaldehyde starter compound or the

Suspending agent is added before or after drying,

(β) in order to activate the DMC catalyst in the presence of the polymeric formaldehyde initiator compound, a partial amount (based on the total amount of alkylene oxides used in the activation and polymerization) of one or more alkylene oxides is added to the mixture resulting from step (a) wherein this addition of a partial amount of alkylene oxide may optionally be carried out in the presence of further comonomers, in particular CO2, and in which case the temperature peak occurring due to the following exothermic chemical reaction ("hotspot") and / or a pressure drop in the reactor is respectively waited for, and wherein the step (β) for activation can also take place several times, and in the second step (ii)

(γ) one or more alkylene oxides and optionally further comonomers, in particular carbon dioxide, are added to the mixture resulting from step (β), wherein the alkylene oxides used in step (γ) may be the same or different from the alkylene oxides used in step (β) wherein at least one polymeric formaldehyde starter compound is added in at least one of steps (a) and (β).

A process according to claim 6, wherein the polymerization in step (γ) is carried out at a temperature of 70 to 140 ° C.

8. The method according to claim 6 or 7, wherein in step (a) as suspending agent at least one compound selected from the group consisting of 4-methyl-2-oxo-l, 3-dioxolane, l, 3-dioxolan-2-one, Acetone, methyl ethyl ketone, acetonitrile, nitromethane, dimethyl sulfoxide, sulfolane, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dioxane, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, ethyl acetate,

Butyl acetate, pentane, n-hexane, benzene, toluene, xylene, ethylbenzene, chloroform, chlorobenzene, dichlorobenzene and carbon tetrachloride is used.

9. The method according to any one of claims 6 to 8, wherein in step (a)

(al) a suspension agent and the DMC catalyst and water and / or other volatile compounds are removed by at least once, preferably three times with 1 bar to 100 bar (absolute) of an inert gas at a temperature of 90 to 150 ° C. is applied and then each of the overpressure is reduced to about 1 bar to 20 bar (absolute) and in a subsequent step

(a2) to the mixture of step (a), the formaldehyde-initiator compound is added.

10. A polyoxymethylene block copolymer obtainable by a process according to any one of claims 1 to 9.

11. Polyoxymethylene block copolymer according to claim 10 having a polydispersity index <2.5.

12. Polyoxymethylene-polyoxyalkylene carbonate block copolymer comprising an inner polyoxymethylene block ("starter") and at least one outer polyoxyalkylene carbonate block according to formula (II)

wherein R is an organic radical such as alkyl, alkylaryl, arylalkyl or aryl, which may each contain heteroatoms such as O, S, Si, etc., and wherein a, b, and c are an integer number and R are in different Repeating units, and wherein the structural unit "starter" represents a polyoxymethylene block resulting from the polymeric formaldehyde starter compound.

13. Polyurethane polymer obtainable by reacting a di-, tri- and / or polyisocyanate with at least one polyoxymethylene block copolymer according to one of claims 10 to 12.

14. Flexible polyurethane foam or rigid polyurethane foam obtainable by reacting a di-, tri- and / or polyisocyanate with at least one polyoxymethylene block copolymer according to one of claims 10 to 12.

15. Use of polyoxymethylene block copolymers according to one or more of claims 10 to 12 for the production of polyurethanes, detergent and cleaner formulations, drilling fluids, fuel additives, ionic and nonionic surfactants, lubricants, process chemicals for the paper or textile production or cosmetic formulations